newr2006

ALTER TABLE distributors ADD COLUMN address varchar(30);

从表中删除一个字段：

ALTER TABLE distributors DROP COLUMN address RESTRICT;

在一个操作中修改两个现有字段的类型：  

ALTER TABLE distributors
    ALTER COLUMN address TYPE varchar(80),
    ALTER COLUMN name TYPE varchar(100);

使用一个 USING 子句，   把一个包含 UNIX 时间戳的 integer 字段转化成 timestamp with time zone：

ALTER TABLE foo
    ALTER COLUMN foo_timestamp TYPE timestamp with time zone
    USING
        timestamp with time zone 'epoch' + foo_timestamp * interval '1 second';

对现存字段改名：

ALTER TABLE distributors RENAME COLUMN address TO city;

更改现存表的名字∶

ALTER TABLE distributors RENAME TO suppliers;

给一个字段增加一个非空约束：

ALTER TABLE distributors ALTER COLUMN street SET NOT NULL;

从一个字段里删除一个非空约束：

ALTER TABLE distributors ALTER COLUMN street DROP NOT NULL;

给一个表增加一个检查约束：

ALTER TABLE distributors ADD CONSTRAINT zipchk CHECK (char_length(zipcode) = 5);

删除一个表和它的所有子表的监查约束：

ALTER TABLE distributors DROP CONSTRAINT zipchk;

向表中增加一个外键约束：

ALTER TABLE distributors ADD CONSTRAINT distfk FOREIGN KEY (address) REFERENCES addresses(address) MATCH FULL;

给表增加一个（多字段）唯一约束：

ALTER TABLE distributors ADD CONSTRAINT dist_id_zipcode_key UNIQUE (dist_id, zipcode);

给一个表增加一个自动命名的主键约束，要注意的是一个表只能有一个主键：

ALTER TABLE distributors ADD PRIMARY KEY (dist_id);

把表移动到另外一个表空间：

ALTER TABLE distributors SET TABLESPACE fasttablespace;

把表移动到另外一个模式：

ALTER TABLE myschema.distributors SET SCHEMA yourschema;

好的代码，自然要保存：

代码

private static readonly Regex REGEX_LINE_BREAKS = new Regex(@"\n\s*", RegexOptions.Compiled);
private static readonly Regex REGEX_LINE_SPACE = new Regex(@"\n\s*\r", RegexOptions.Compiled);
private static readonly Regex REGEX_SPACE = new Regex(@"( )+", RegexOptions.Compiled);

protected override void Render(HtmlTextWriter writer)
{
    using (HtmlTextWriter htmlwriter = new HtmlTextWriter(new System.IO.StringWriter()))
    {
        base.Render(htmlwriter);
        string html = htmlwriter.InnerWriter.ToString();
        html = REGEX_LINE_BREAKS.Replace(html, string.Empty);
        html = REGEX_LINE_SPACE.Replace(html, string.Empty);
        html = REGEX_SPACE.Replace(html, " ");
        writer.Write(html.Trim());
    }
}

提前两天发邮件，

public static void SendMail(object sender, ElapsedEventArgs e)
        {          
            foreach (KeyValuePair<string, System.Timers.Timer> keyValuePair in Globals.TimerLists)
            {
                if (keyValuePair.Value == sender)
                {
                    string machineId = keyValuePair.Key;
                    using (Database accessor = new Database())
                    {
                        CheckOutInfo info = accessor.SelectCheckoutRecord(machineId);
                        if(info == null)
                        {
                            return;
                        }
                        //info.DueDate is expriation day
                        TimeSpan diff = DateTime.Now.Subtract(info.DueDate) + new TimeSpan(2, 0, 0, 0, 0);
                        diff = diff.Add(new TimeSpan(1, 0, 0)); // Add 1 hour to ignore the short time elapsed during processing.

                        // reSet the interval to let timer trigger next day.
                        if (diff.TotalDays < 0)
                        {
                            Debug.WriteLine("diff.Seconds< 0");
                            System.Timers.Timer reminderTimer = (System.Timers.Timer)sender;
                            reminderTimer.Interval = GetNextTriggerInterval(info.DueDate);
                            Debug.WriteLine(reminderTimer.Interval.ToString());
                            reminderTimer.AutoReset = false;
                            reminderTimer.Enabled = true;
                            break;
                        }
                        //Email reminder should be sent from 2 days before expiration;
                        else if (diff.TotalDays <= 2.0 && diff.TotalDays>=0.0)
                        {
                            VM vm = ShareFactory.GetVMByID(new Guid(machineId));
                            if (vm != null)
                            {
                                System.Timers.Timer reminderTimer = (System.Timers.Timer)sender;
                                reminderTimer.Interval = GetNextTriggerInterval(info.DueDate);
                                Debug.WriteLine(reminderTimer.Interval.ToString());
                                reminderTimer.AutoReset = false;
                                reminderTimer.Enabled = true;

                                string  Language = accessor.GetMachineLanguage(machineId);
                                ReservePolicy reservePolicy = ConfigurationFactory.GetReservePolicy(info.ReserveType);
                                if (info.ExtendTimes < reservePolicy.ExtendTimes)
                                {
                                    Debug.WriteLine("SendExpireEmail");                                 
                                }
                                else
                                {
                                    Debug.WriteLine("SendCheckinEmail");
                                 
                                }
                            }
                            else
                            {
                                // Machine does not exist. Just delete the records.
                               Debug.WriteLine("Machine does not exist. Just delete the records.");                             
                                Globals.TimerLists.Remove(machineId);
                            }

                        }
                        else
                        {
                             Debug.WriteLine("CheckIn");                           
                        }
                    }

                    break;
                }
            }
        }